The objective of this Phase II SBIR project is to qualify the permanent aortic balloon pump for clinical trial in intractable left ventricular failure (LVF). The system provides a distinctive balance of benefits and low risk so that in Phase III, it is expected to earn a niche among therapies for chronic congestive LVF. The permanent aortic balloon system supports the left ventricle at therapeutically effective levels while maximizing patient safety. It is unique among left ventricular assist systems in that its continuous pumping action is nonobligatory. The patient can be untethered for hours. During Phase I, the redesigned blood pump was successfully tested in 5 calves pumped intermittently without anticoagulant therapy over a 6 week period. These results lead to Phase II in which our specific aims are: 1. To confirm and quantitate hemodynamic effects of the permanent aortic balloon in calves in which acute heart failure has been induced. 2. To characterize the performance limits of the system. 3. To demonstrate in vitro component reliability over a 2-year design life. 4. To test and document the reliability and safety of the system in long-term (6 month) test in each of 8 animals. 5. To develop an investigational plan, protocols and consent form that will warrant approval by the hospital IRB and FDA for trial in human subjects.